Sound designers rarely shape a raw waveform directly — they shape its loudness envelope: the curve that multiplies a sound's amplitude over time. A four-stage Attack–Decay–Sustain–Release (ADSR) envelope is the standard model, piecewise linear in time t since the trigger (A, D, R in seconds, S in [0,1]):
0 ≤ t < A: L(t) = t / A (Attack: silence → peak)
A ≤ t < A+D: L(t) = 1 − (1−S)·(t−A) / D (Decay: peak → sustain)
held, t ≥ A+D: L(t) = S (Sustain: held level)
after release, τ: L(t) = S · (1 − τ / R) (Release: fade to silence)
The article's core claims about perception map directly onto these four numbers:
- Fast Attack (≈10–40 ms) reproduces a sharp transient — the "sudden, sharp sound" that grabs attention immediately, like a gunshot or door slam.
- Slow Attack (hundreds of ms – seconds) reads as a gradual swell — the "prolonged, subtle effect" the article says builds unease or tension, like a horror drone rising under a scene.
- Sustain level sets how loud the effect sits once it has settled — high sustain reads as a continuous ambient layer, low sustain reads as a transient hit that has already mostly decayed.
- Release controls how a sound trails off after the trigger is let go — a long release leaves a tail (reverb-like), a short one cuts cleanly.
Controls: press and hold the trigger button (or press Space) to fire the envelope — it runs Attack → Decay → Sustain while held, then Release the instant you let go, exactly like a synthesizer key or a game engine's one-shot cue. The 3D impact sphere scales and glows with L(t); the scrolling bar history behind it is a live loudness-over-time readout, colour-coded by phase.